Uretonimine-Modified Isocyanate Composition and Method of Forming the Same

ABSTRACT

A uretonimine-modified isocyanate composition has reduced color. The uretonimine-modified isocyanate composition comprises a polyisocyanate composition having two or more isocyanate groups and comprising 4,4′-diphenylmethane diisocyanate (MDI) and a catalyst for catalyzing a reaction of the isocyanate groups to form carbodiimides available for forming uretonimines and uretonimine oligomers. A first quenching agent partially quenches the reaction of the isocyanate groups to inhibit formation of the carbodiimides thereby inhibiting additional formation of uretonimines and uretonimine oligomers and a second quenching agent different than the first quenching agent quenches the reaction of the isocyanate groups to further inhibit formation of the carbodiimides thereby further inhibiting additional formation of uretonimines and uretonimine oligomers. A method of forming the uretonimine-modified isocyanate composition is also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/276,702, filed Mar. 10, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention relates to a uretonimine-modified isocyanatecomposition and method of forming the same. More specifically, thesubject invention relates to a uretonimine-modified isocyanatecomposition having reduced color and a method of forming theuretonimine-modified isocyanate composition having the reduced color.

2. Description of the Related Art

Various uretonimine-modified isocyanate compositions, also known ascarbodiimide-modified isocyanate compositions, are known. Thesecompositions generally comprise a polyisocyanate composition having twoor more isocyanate groups and comprising 4,4′-diphenylmethanediisocyanate (MDI) and a catalyst for catalyzing a reaction of theisocyanate groups to form carbodiimides. The carbodiimides then reactwith available isocyanate groups to form uretonimines that undergofurther reaction to form uretonimine oligomers. Once the reaction hasachieved a desired level, generally based upon a percent NCO groupsremaining, a quenching agent is added to quench the catalyst used topromote the reaction of the isocyanate groups, thus inhibiting theformation of additional carbodiimides thereby inhibiting additionalformation of uretonimine and uretonimine oligomers. Examples ofquenching agents that have been employed include strong acids, such astrifluoromethane sulfonic acid or perchloric acid in U.S. Pat. No.4,260,554. Other examples include weaker acids, such as Lewis acids,aromatic carboxylic acid halides, aromatic sulfonic acid esters and thelike in U.S. Pat. No. 4,120,884.

Generally, it has been known to quench the reaction with a very strongacid to prevent, inhibit, or retard continued reaction of the isocyanategroups over time and to prevent the continued formation of carbodiimideand uretonimine oligomers. However, the addition of the strong acidresults in the uretonimine-modified composition becoming colored,typically yellow, orange, or brown. Any isocyanate products or articlesformed from the colored uretonimine-modified composition generally havethe same color. Therefore, the articles may require additionalprocessing to disguise the color or additional amounts of pigment arenecessary to overcome the prior color of the uretonimine-modifiedcomposition.

The weaker acids, while affording lower color uretonimine-modifiedcompositions, generally do not adequately deactivate the catalyst.Therefore, the stability of the composition is undesirable and thecomposition must be used within a shorter period of time. If thecomposition is used after the stability of the composition has beencompromised, then articles formed therefrom are susceptible to beingrejected as non-conforming.

Accordingly, it would be advantageous to provide a composition thatovercomes the inadequacies that characterize the related art.

SUMMARY OF THE INVENTION

The subject invention provides a uretonimine-modified isocyanatecomposition having reduced color and a method of forming the same. Theuretonimine-modified isocyanate composition comprises a polyisocyanatecomposition having two or more isocyanate groups and comprising4,4′-diphenylmethane diisocyanate (MDI) and a catalyst for catalyzing areaction of the isocyanate groups to form carbodiimides that undergofurther reaction to form uretonimine oligomers. A first quenching agentpartially quenches the reaction of the isocyanate groups to inhibitformation of the carbodiimides, uretonimines and uretonimine oligomersand a second quenching agent different than the first quenching agentquenches the reaction of the isocyanate groups to further inhibitformation of the carbodiimides, uretonimines and uretonimine oligomersand provide a storage stable composition.

Formation of the uretonimine-modified composition according to thesubject invention results in the composition having reduced color andexhibiting good storage stability. As compared to related art processesand composition, the uretonimine-modified isocyanate composition can beused to produce articles that have little color. Thus, lower amounts ofpigments, if any at all, will be needed to produce colored articles orto disguise the coloration of the uretonimine-modified isocyanatecomposition. Additionally, the composition of the subject inventionperforms adequately in stability testing and outperforms commerciallyavailable uretonimine-modified isocyanate compositions.

DETAILED DESCRIPTION OF THE INVENTION

A method of producing a uretonimine-modified isocyanate composition isdisclosed. The method of producing the uretonimine-modified isocyanatecomposition includes the step of providing a polyisocyanate compositionhaving two or more isocyanate groups and comprising 4,4′-diphenylmethanediisocyanate (MDI). It is known that 4,4′-MDI is also referred to asbis(4-isocyanatophenyl)methane or 4,4′-methylenediphenyl diisocyanate.As used herein, the terms “isocyanate composition” and “composition” areintended to refer to the uretonimine-modified isocyanate composition.

The 4,4′-MDI is present in an amount of from about 1 to less than 99.5parts by weight based on 100 parts by weight of the polyisocyanatecomposition. Preferably, the 4,4′-MDI is present in an amount of fromabout 35 to about 98 parts by weight, and more preferably from about 50to about 98 parts by weight, both based on 100 parts by weight of thepolyisocyanate composition. It is to be appreciated that differentamounts of the 4,4′-MDI will generally produce different types ofuretonimine-modified isocyanate compositions. The 4,4′-MDI can beproduced by any of the commonly employed processes including thedistillation of crude mixtures of isocyanate obtained by phosgenating amixture of polyamines generally obtained by acid condensation of anilineand formaldehyde.

Generally, in addition to the 4,4′-MDI, the polyisocyanate compositionmay also comprise 2,4′-MDI, 2,2′-MDI, and other isomers. The 2,4′-MDIand the 2,2′-MDI isomers are less reactive than the 4,4′-MDI and whencombined with 4,4′-MDI in certain ratios afford compositions that areliquids at room temperature. It has previously been known to add smallamounts of either the 2,4′-MDI and the 2,2′-MDI to the 4,4′-MDI toimprove the stability of the polyisocyanate composition. For example,commercially pure 4,4′-MDI has about 98 parts by weight 4,4′-MDI and upto 2 parts by weight 2,4′-MDI. The subject invention provides the2,4′-MDI present in an amount of greater than 0.5 to about 60 parts byweight based on 100 parts by weight of the polyisocyanate composition.Preferably, the 2,4′-MDI is present in an amount of from about 1 toabout 50 parts by weight, and more preferably, from about 2 to about 40parts by weight, both based on 100 parts by weight of the polyisocyanatecomposition

To form the uretonimine-modified isocyanate composition, thepolyisocyanate composition is reacted at a temperature of greater thanabout 80° C., preferably from about 80° C. to about 130° C., and morepreferably from about 100° C. to about 120° C. The temperature of thepolyisocyanate composition may be raised using standard techniques, suchas heat baths, ovens, burners, etc.

The polyisocyanate composition is also reacted in the presence of acatalyst such that the isocyanate groups of MDI react to first formcarbodiimides. The catalyst is present in amounts of from about 2 toabout 500 parts per million. The amount of catalyst depends on thereaction temperature such that the reaction temperature remains near thedesired reaction temperature and that the reaction occurs in a desiredamount of time. Preferably, the catalyst is present in an amount of fromabout 5 to about 100 parts wherein a, b, c and d are each selected fromone of hydrogen or hydrocarbyl from 1 to 12 carbon atoms inclusive, R isselected from one of lower alkyl or aryl and X is selected from one ofoxygen or sulfur.

Representative compounds within this class of catalysts are3-methyl-1-phenyl-3-phospholene-1-oxide,3-methyl-1-phenyl-2-phospholene-1-oxide, 1-methyl-3-phospholene-1-oxide,1-methyl-2-phospholene-1-oxide, 1-ethyl-3-phospholene-1-oxide,1-ethyl-2-phospholene-1-oxide 1-phenyl-3-phospholene-1-oxide, and1-phenyl-2-phospholene-1-oxide. Also, polymer bound catalysts, andespecially polymer bound phospholene oxides, may be employed in thesubject invention.

In addition, co-catalysts may also be used to ensure the desiredreaction temperature and time. The co-catalyst is added in an amount offrom about 50 to about 1500 parts per million, preferably from about 100to about 1250, more preferably from about 200 to about 1000 parts permillion. The co-catalyst is preferably a phosphite, comprised ofaliphatic, aromatic, or mixed aliphatic and aromatic groups. Examples ofpreferred co-catalysts include triphenyl phosphite, tributyl phosphite,phenyl diisodecyl phosphite, and diphenyl isodecyl phosphite.

In addition, hindered phenol antioxidants, and especially2,6-di-tert-butyl-hindered phenolic antioxidants, may be present in thepolyisocyanate composition. Examples of phenolic antioxidants include2,6-di-tert-butyl-4-methylphenol, also known as BHT, and3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, available commerciallyas Irganox® 1076. Hindered phenolic antioxidants are commonly used asstabilizers for commercial polyisocyanate compositions, and thus may bepresent when employed in per million. As appreciated by those ofordinary skill in the art, the catalyst may participate in the reactionand may also remain in the uretonimine-modified isocyanate composition.Alternatively, the catalyst may be removed or filtered. The catalystcatalyzes the formation of the carbodiimides and does not substantiallyinteract with the reaction of the carbodiimides and the polyisocyanatecomposition or the uretonimines.

The uretonimine-modified compositions of the present invention may beprepared using any of the known carbodiimide-promoting compounds as thecatalyst. The catalyst is selected from at least one of phospholene,phospholene oxide, phospholidine, phospholidine oxide, phosphate esters,and phosphine oxides. One example of a phospholidine includes 1-phenylphospholidine and one example of a phospholidine oxide includes1-phenyl-phospholidine-1-oxide. Other suitable catalysts includephosphate esters, such as triethylphosphate, and phosphine oxides, suchas tributylphosphine oxide.

Preferred catalysts are phospholene oxides, and most preferred arephospholene 1-oxides having the following formula:

Or the isomeric formula

forming the uretonimine-modified isocyanate composition of the subjectinvention. If the hindered phenolic antioxidants are not present in thepolyisocyanate composition, then they may also be added before or afterthe reaction to form carbodiimide, uretonimine, and uretonimineoligomers.

It is to be appreciated by those of ordinary skill in the art that onlya portion of the isocyanate groups may react to form the carbodiimides,however, all isocyanate groups may react. The carbodiimides can thenreact further with the isocyanate groups of unreacted MDI to formuretonimine and uretonimine oligomers.

Alternatively, the carbodiimide may also react with the isocyanate groupof another molecule of uretonimine instead of unreacted MDI, to form ahigher molecular weight, oligomeric uretonimine. For clarity, the term“uretonimine” is intended to mean 3-functional, six ring uretonimineoligomer because there is a single uretonimine group, as shown below.Additionally, “uretonimine oligomers” is intended to mean more than 3functional groups, which have more than a single uretonimine group, asshown below.

The MDI forms uretonimines and uretonimine oligomers as a result of thereaction. In addition to reacting with MDI, other mono-, di-, tri-,tetra-isocyanates and other aromatic, aliphatic, and cycloaliphaticpolyisocyanates and combinations thereof may react with the MDI.Examples of suitable monoisocyanates include phenyl isocyanates andcyclohexyl isocyanate. Examples of suitable diisocyanates includem-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluenediisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate,hexamethylene diisocyanate, tetramethylene diisocyanate,cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate (andisomers), isophorone diisocyanate, hydrogenated diphenylmethanediisocyanate, naphthalene-1,5 diisocyanate,1-methoxyphenyl-2,4-diisocyanate, 4,4′-biphenylene diisocyanate,3,3′-dimethoxy-4,4′-biphenyl diisocyanate,3,3′-dimethyl-diphenylmethane4,4′-diisocyanate, and tetramethylxylylenediisocyanate. Examples of suitable triisocyanates include4,4′,4″-triphenylmethane triisocyanate and toluene 2,4,6-triisocyanate.Examples of suitable tetraisocyanates include4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate and examples ofsuitable polymeric polyisocyanates include polymethylene polyphenylenepolyisocyanate.

The uretonimines formed in the reaction are a mixture of oligomers,including 3-functional, six ring uretonimine, 4-functional, ten ringuretonimine, and 5-functional, fourteen ring uretonimine. One possiblereaction of the 4,4′-MDI while in the presence of the catalyst is shownbelow, which results in the formation of the 3-functional, six ringoligomer,1,3-bis(4-(4-isocyanatobenzyl)phenyl)-4-(4-(4-isocyanatobenzyl)phenylimino)-1,3-diazetidin-2-one.The first step in this reaction is the formation of a carbodiimideintermediate, N,N′-methanediylidenebis-4-(4-isocyanatobenzyl)anilinefrom two molecules of 4,4-MDI. The carbodiimide may react further withanother molecule of 4,4′-MDI to form a 3-functional, six ringuretonimine.

Below is an example of the 4-functional, ten ring uretonimine oligomerthat may be formed as a result of the 3-functional uretonimine oligomerreacting with the carbodiimide of 4,4′-MDI.

Below is an example of the 5-functional, fourteen ring uretonimineoligomer that may be formed as a result of the 4-functional uretonimineoligomer reacting with the carbodiimide of 4,4′-MDI.

The longer the reaction proceeds, the larger the amount of thehigher-functional uretonimine oligomers, i.e., greater than3-functional, that is formed. As more MDI is consumed and converted touretonimines, the isocyanate value of the polyisocyanate composition isreduced because reactive isocyanate groups are reacted with one another.As understood by those of ordinary skill in the art, the isocyanatevalue refers to a weight percentage of reactive isocyanate groups in thepolyisocyanate composition. The isocyanate value can be determined bythe following, well-known equation:

${{{Iscocyanate}\mspace{14mu} {Value}} = {{\% \mspace{14mu} {NCO}\mspace{14mu} {groups}} = {\frac{42 \times f}{Mw} \times 100}}},$

wherein 42 is the molecular weight of the NCO groups, f is functionalityand refers to the number of reactive groups in the polyisocyanatecomposition, and Mw is the molecular weight of the polyisocyanate. Forexample, 4,4′-MDI has a molecular weight of 250.26 and a functionalityof 2 resulting in the isocyanate value, or % NCO groups, of 33.6.

The reaction of the polyisocyanate composition is then quenched.Generally, it has been known to quench the reaction with a very strongacid to prevent, inhibit, or retard continued reaction of the isocyanategroups over time and to prevent the continued formation of additionalcarbodiimide and uretonimine and uretonimine oligomers during storage ofthe composition. However, the addition of the very strong acid resultsin the uretonimine-modified composition becoming colored, typicallyyellow, orange, or brown. Other known processes for producinguretonimine-modified compositions also result in the compositionbecoming yellow, such as high reaction temperature with other catalysts.Any articles formed from the colored uretonimine-modified compositiongenerally have the same color. If the article is to be a differentcolor, additional amounts of pigment are necessary to overcome the priorcolor of the uretonimine-modified composition.

Formation of the uretonimine-modified composition according to thesubject invention results in the composition having reduced or lowcolor. It has been determined that dual quenching reduces the formationof the color in the uretonimine-modified composition. More specifically,dual quenching with a first quenching agent followed by a secondquenching agent different than the first quenching agent is preferred.The first quenching agent partially quenches the reaction of theisocyanate groups to inhibit formation of carbodiimides therebyinhibiting formation of the uretonimine and uretonimine oligomers andthe second quenching agent further quenches the reaction to furtherinhibit formation of carbodiimides thereby inhibiting additionalformation of the uretonimine and uretonimine oligomers.

The addition of the first quenching agent occurs when the polyisocyanatecomposition is at a temperature of greater than about 80° C. Preferably,the first quenching agent is added as the polyisocyanate compositioncontinues to react at a first temperature from about 80° C. to about130° C. The temperature of the polyisocyanate composition is thenreduced to a second temperature lower than the first temperature and thesecond quenching agent is added. Preferably, the second temperature isless than about 80° C. More preferably, the second temperature is in arange of from about 28° C. to about 75° C. Said another way, once thepolyisocyanate composition has reached the second temperature in thisrange, the second quenching agent is added. The reduction of thetemperature may occur by removing from a heat source or by activecooling as understood by those of skill in the art.

The dual quenching stages reduce the coloration of theuretonimine-modified composition. In this manner, theuretonimine-modified composition can be formed that is low color ornearly colorless. The advantages of a low color or nearly colorlesscomposition are numerous. First, any articles formed therefrom will alsobe low color or nearly colorless allowing for a more aestheticallypleasing article that has many more uses. Second, if the article is tobe colored, it is likely that lower amounts of pigments will be requiredsince the base composition is nearly colorless.

In order to reduce coloration, the first quenching agent has a pKagreater than the second quenching agent. Preferably, the first quenchingagent is a first acid or acid generator having a pKa of greater thanabout −8.0. It is to be appreciated by those of ordinary skill in theart that the term “acid generator” refers to compositions that are ableto generate an acid when exposed to nucleophilic substances, such aswater, amines, ureas, alcohols, etc. One example of an acid generator isbenzoyl halide, which generates hydrochloric acid when exposed tonucleophiles.

The first acid or acid generator is selected from at least one inorganicacid, carboxylic acid, peroxides, sulfinic acid, sulfonic acid, sulfonicacid halides and carboxylic acid halides. It is to be appreciated thatthe first acid or acid generator may include a solvent for dispersingthe acid or acid generator, such as diisodecyl adipate, diethylmalonate, or the like. Suitable examples of the first acid or acidgenerator include, but are not limited to, hydrochloric acid,methanesulfonic acid, toluenesulfonic acid, sulfuric acid, sulfonicacid, acetic acid, oxalic acid, citric acid, formic acid, ascorbic acid,benzoic acid, thiophenol, peracetic acid, benzoyl chloride, and mixturesthereof. For example, methanesulfonic acid has a pKa of about −2.6,benzoic acid has a pKa of about 4.2, and hydrochloric acid has a pKa ofabout −8.0.

The amount of the first acid or acid generator may depend upon theamount and the type of catalyst used to catalyze the reaction. However,it is preferred that the first acid or acid generator is present in anamount of from about 1 to about 500 parts per million based on theuretonimine-modified isocyanate composition. More preferably, the firstquenching agent is present in an amount of from about 1 to about 100parts per million based on the uretonimine-modified isocyanatecomposition.

The second quenching agent is also preferably a second acid or acidgenerator having a pKa of less than about −8.0. The second acid or acidgenerator is selected from at least one of trifluoromethanesulfonic acidand perchloric acid. It is to be appreciated that the second acid oracid generator may include a solvent for dispersing the acid or acidgenerator. Trifluoromethanesulfonic acid has a pKa of about −13 to about−14 and perchloric acid has a pKa of about −10. It is to be appreciatedthat other very strong second acids could also be used.

The second acid or acid generator is present in an amount of from about1 to about 250 parts per million based on the uretonimine-modifiedisocyanate composition. Preferably, the second quenching agent ispresent in an amount of from about 1 to about 75 parts per million basedon the uretonimine-modified isocyanate composition.

The following examples illustrate the production of theuretonimine-modified isocyanate composition, according to the subjectinvention and illustrating certain properties of theuretonimine-modified isocyanate composition, as presented herein, areintended to illustrate and not limit the invention.

EXAMPLES

A uretonimine-modified isocyanate composition is produced from acomposition comprising the components according to Table 1 for Example 1and Comparative Example A. The components that form the composition arelisted in parts by weight, unless otherwise indicated.

TABLE 1 4,4′-MDI 93.50 2,4′-MDI 6.50

To a 1-L round-bottomed flask equipped with mechanical stirrer, 58.5 gLupranate® MI Isocyanate (about 48 wt % 4,4′-MDI and 52 wt % 2,4′-MDI),commercially available from BASF Corporation, is charged under inertatmosphere and preheated to 60° C. Next, 591.5 g of Lupranate® MIsocyanate (about 98 wt % 4,4′-MDI and 2 wt % 2,4′-MDI), commerciallyavailable from BASF Corporation, and 0.0722 g of a 5% solution ofphospholene oxide catalyst in methyl ethyl ketone is added. Thetemperature is raised to about 105° C. and the reaction mixture isstirred for about 3.25 hours.

Next, Comparative Example A is prepared by transferring 100 g of thereaction mixture to a glass bottle preheated to about 105° C. and 0.0344g of a 16.6% solution of trifluoromethane sulfonic acid (TFMSA) indiethyl malonate (Comparative Example A) is added to the glass bottle.The TFMSA is the strong acid used to deactivate the reaction. Two other100-g samples are removed from the flask and are not further discussed.

Example 1 is prepared by adding 0.1644 g of a 23.51% solution of benzoylchloride in diisodecyl adipate (the first quenching agent) to the 344 gof product remaining in the flask and heating is discontinued. When theproduct cools to about 40° C., 90 g of the product is transferred to aglass bottle containing 0.0317 g of a 16.6% solution of TFMSA in diethylmalonate (the second quenching agent).

Table 2 summarizes the color assessments for Comparative Example A andExample 1. The color of liquid isocyanate products are measured with aBYK Gardner Model LCSII Colorimeter. The Colorimeter measures colorspectrophotometrically, in tristimulus values, either XYZ or CIE L*a*b*(CIELAB). The tristimulus values can be converted to a color measurementvalue in a wide variety of conventional color scales including thePlatinum-Cobalt Scale, APHA, and yellowness index. The color of MDIuretonimine samples is reported in the APHA color scale and higher APHAvalues represent a darker yellow color.

TABLE 2 Color Assessment Stage 2 catalyst Stage 1 catalyst QuenchingAPHA Quenching Agent ppm Agent ppm Color Comparative TFMSA 57.1 — — 643Example A Example 1 Benzoyl chloride 112.3 TFMSA 58.4 377

From Table 2, Comparative Example A has an increased APHA color overExample 1. Thus, Comparative Example A is a more darker yellow thanExample 1.

Other uretonimine-modified isocyanate compositions are produced from acomposition comprising the components according to Table 3 for Example 2and Comparative Example B. The components that form the compositions arelisted in parts by weight, unless otherwise indicated.

TABLE 3 Comparative Example 2 Example B 4,4′-MDI 93.50 93.50 2,4′-MDI6.50 6.50

In Example 2, a 500-mL round-bottomed flask equipped with mechanicalstirrer, heat mantle and digital temperature controller is preheated to60° C. and charged with 358.7 g of Lupranate® M Isocyanate under inertatmosphere. Next, 0.0291 g of a 4.78% solution of phospholene oxidecatalyst in γ-butyrolactone is added and the temperature is raised to105° C. and the reaction mixture is stirred for about 3.5 hours. To thereaction mixture, 0.0465 g of a 12.45% solution of methanesulfonic acid(MSA) in diethyl malonate (the first quenching agent) is added andheating is discontinued. When the product temperature has fallen to 50°C., 0.1663 g of an 11.55% solution of TFMSA in diethyl malonate (thesecond quenching agent) is added. The intermediate % NCO is 28.88.Another 25.88 g of Lupranate® M isocyanate is added to bring the final %NCO of the product to 29.2.

In Comparative Example B, a 500-mL round-bottomed flask equipped withmechanical stirrer, heat mantle and digital temperature controller ispreheated to 60° C. and charged with 309.7 g Lupranate® M Isocyanateunder inert atmosphere. To this is added 0.3116 g triphenyl phosphiteand 0.0341 g of a 5% solution of phospholene oxide catalyst in methylethyl ketone. The temperature is raised to 105° C. and the reactionmixture is stirred for 2.51 hours. Next, 0.0824 g of an 11.05% solutionof TFMSA in diisodecyl adipate is added and heating was discontinued.When the product temperature had fallen to 50° C., an additional chargeof 0.0560 g TFMSA solution is added. The intermediate % NCO value was28.48. Another 50.23 g Lupranate® M Isocyanate was added to bring thefinal % NCO of the product to 29.2. Similarly to Table 2, Example 2 andComparative Example B under went a color analysis using the colorimeterdescribed above and the results are summarized in Table 4 below.

TABLE 4 Color Assessment Stage 1 catalyst Quenching Stage 2 catalystAPHA Agent ppm Quenching Agent ppm Color Example 2 MSA 16.4 TFMSA 55.1276 Comparative TFMSA 30.3 TFMSA 20.4 567 Example B

Again, Example 2 formed from the dual stage process with the firstquenching agent having a pKa greater than the second quenching agent hasa lower APHA color than Comparative Example B. In other words, Example 2has less color than Comparative Example B.

In addition to reducing and/or eliminating color, it is important thatthe catalyst present in the uretonimine-modified isocyanate compositionis sufficiently deactivated. When the quenching agent does notadequately deactivate the catalyst, the stability of theuretonimine-modified composition decreases. Therefore, the combinationof the first and the second quenching agents must adequately stabilizethe uretonimine-modified isocyanate composition.

Table 5 illustrates the formation of uretonimine-modified isocyanatecomposition having employed the quenching agents as shown. Thepolyisocyanate composition is Lupranate® M isocyanate and the processused for preparing the uretonimine-modified isocyanate composition issimilar to that used in Example 2 and Comparative Example 2.Compositions in Examples 2-7 were prepared using a first quenching agentand a second quenching agent. Comparative example C, D, and E wereprepared using only a first quenching agent.

In order to determine stability, the following examples were subjectedto an accelerated test. The accelerated test simulates the long-termstorage stability of MDI-based uretonimine products at ambienttemperatures. For each example, a sample of the uretonimine-modifiedisocyanate composition is placed in a sealed plastic container and thenstored in an 80° C. oven for 7 days. At the end of the testing period,the % NCO of the sample is measured and compared with the initial(pre-test) % NCO value. The % decrease in % NCO value is the measure ofproduct stability. Acceptable stability is defined as a decrease in %NCO of about 4% or less. Samples judged to be unstable generally had adecrease in % NCO of 6% or higher. In some cases, the sample gelled orsolidified after the 7-day testing, which indicated the sample wasextremely unstable. It is to be appreciated that it is desirable for anyuretonimine-modified isocyanate composition formed according to theinvention to have a % NCO decrease of less than 6% for the shelf life ofthe product. The shelf-life may vary depending upon certainapplications, but is likely to not exceed more than five years.

TABLE 5 Stage 1 (105°) Stage 2 (50°) % Stability Quenching Quenchingdecrease Test Agent ppm Agent ppm in % NCO Result Example 3 Benzoyl108.5 TFMSA 64.5 2.4 Pass chloride Example 4 H₂SO₄ 25.8 TFMSA 20 3.1Pass Example 5 MSA 17.5 TFMSA 25 3.0 Pass 35 3.2 Pass 50.5 2.7 PassExample 6 MSA 15.9 TFMSA 30.8 2.9 Pass Example 7 MSA 18.1 TFMSA 47.1 3.6Pass Comparative TFMSA 51.5 — — 3.2 Pass Example C Comparative Benzoyl108.5 — — Sample Fail Example D chloride gelled Comparative MSA 43 — —25.1  Fail Example E

Examples 3-7 were formed with the first and second quenching agents andpass the stability test. Additionally, the % decrease in % NCO of theseexamples was as good as or better than the conventionaluretonimine-modified isocyanate composition of Comparative Example C.The advantages of the subject invention over the traditional processingmethods are evident in the lower color and equivalent or improvedstability.

For reference, Comparative Examples D and E are given in which 100% of aweaker acid is used to deactivate the catalyst as the sole quenchingagent. These examples failed the stability test indicating that a verystrong catalyst deactivator is necessary to ensure long-term productstability.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A uretonimine-modified isocyanate composition having reduced color,said uretonimine-modified isocyanate composition comprising: apolyisocyanate composition having two or more isocyanate groups andcomprising 4,4′-diphenylmethane diisocyanate (MDI); a catalyst forcatalyzing a reaction of said isocyanate groups to form carbodiimidesavailable for forming uretonimines and uretonimine oligomers; a firstquenching agent having a pKa of greater than about −8.0 for partiallyquenching the reaction of said isocyanate groups to inhibit formation ofcarbodiimides thereby inhibiting additional formation of the uretonimineand uretonimine oligomers; and a second quenching agent different thansaid first quenching agent and having a pKa of less than about −8.0 forquenching the reaction of said isocyanate groups to further inhibitformation of the carbodiimides thereby further inhibiting additionalformation of uretonimines and uretonimine oligomers.
 2. A composition asset forth in claim 1 wherein said first quenching agent is present in anamount of from about 1 to about 500 parts per million based on saiduretonimine-modified isocyanate composition.
 3. A composition as setforth in claim 2 wherein said second quenching agent is present in anamount of from about 1 to about 250 parts per million based on saiduretonimine-modified isocyanate composition.
 4. A composition as setforth in claim 3 wherein said first acid or acid generator is selectedfrom at least one inorganic acid, carboxylic acid, peroxides, sulfinicacid, sulfonic acid, sulfonic acid halides and carboxylic acid halides.5. A composition as set forth in claim 3 wherein said first acid or acidgenerator is selected from at least one of hydrochloric acid,methanesulfonic acid, toluenesulfonic acid, sulfuric acid, acetic acid,oxalic acid, citric acid, formic acid, ascorbic acid, benzoic acid,thiophenol, peracetic acid, and benzoyl chloride.
 6. A composition asset forth in claim 5 wherein said second acid or acid generator isselected from at least one of trifluoromethanesulfonic acid andperchloric acid.
 7. A composition as set forth in claim 5 wherein saidcatalyst is selected from at least one of phospholene, phospholeneoxide, phospholidine, phospholidine oxide, phosphate esters, andphosphine oxides.
 8. A composition as set forth in claim 1 wherein saidfirst quenching agent is present in an amount of from about 1 to about100 parts per million based on the uretonimine-modified isocyanatecomposition.
 9. A composition as set forth in claim 8 wherein saidsecond quenching agent is present in an amount of from about 1 to about75 parts per million based on the uretonimine-modified isocyanatecomposition.
 10. A composition as set forth in claim 1 wherein saidfirst quenching agent includes a solvent.
 11. A composition as set forthin claim 1 wherein said second quenching agent includes a solvent.
 12. Acomposition as set forth in claim 1 wherein said uretonimine-modifiedisocyanate composition has a percentage decrease of NCO value of lessthan 6% when stored in a sealed container and exposed in an oven at 80°C. for 7 days.
 13. A composition as set forth in claim 1 wherein saiduretonimine-modified isocyanate composition has a percentage decrease ofNCO value of less than 4% when stored in a sealed container and exposedin an oven at 80° C. for 7 days.
 14. A composition as set forth in claim1 wherein said uretonimine-modified isocyanate composition has an APHAcolor of less than
 500. 15. A uretonimine-modified isocyanatecomposition having reduced color, said uretonimine-modified isocyanatecomposition comprising: a polyisocyanate composition having two or moreisocyanate groups and comprising 4,4′-diphenylmethane diisocyanate(MDI); a catalyst for catalyzing a reaction of said isocyanate groups toform carbodiimides available for forming uretonimines and uretonimineoligomers; at least one quenching agent; and said uretonimine-modifiedisocyanate composition having a percentage decrease of NCO value of lessthan 6% when stored in a sealed container and exposed in an oven at 80°C. for 7 days.
 16. A composition as set forth in claim 15 wherein saiduretonimine-modified isocyanate composition has an APHA color of lessthan
 500. 17. A uretonimine-modified isocyanate composition havingreduced color, said uretonimine-modified isocyanate compositioncomprising: a polyisocyanate composition having two or more isocyanategroups and comprising 4,4′-diphenylmethane diisocyanate (MDI); acatalyst for catalyzing a reaction of said isocyanate groups to formcarbodiimides available for forming uretonimines and uretonimineoligomers; at least one quenching agent; and said uretonimine-modifiedisocyanate composition having an APHA color of less than
 500. 18. Acomposition as set forth in claim 17 wherein said uretonimine-modifiedisocyanate composition has a percentage decrease of NCO value of lessthan 4% when stored in a sealed container and exposed in an oven at 80°C. for 7 days.